1. Field of the Invention
The invention is concerned with a binocular telescope with eye-pieces set in threaded mounts and having a mutual drive for the simultaneous focusing of both eye-pieces.
2. Prior Art and Technical Considerations
In the case of binocular telescopes which are intended to be waterproof and resistant to tropical conditions the setting of the focal length of the eye-pieces cannot be carried out by means of the eye-piece bridge normally used since, in the case of this design, it is impossible to obtain sufficient sealing between the eye-piece, or eye-piece tube, and the telescope housing. Consequently, in existing binocular telescopes mutual adjustment of both eye-pieces is carried out by means of a so-called central drive. Normally, in the case of this design a driving or focusing gear is arranged on the common or joint axis of the two halves of the telescope and the rotation of this gear is transfered on to focusing rings of the two telescope halves via a gear transmission, thereby producing synchronous focal length adjustment.
In order to carry out diopter adjustment of eye-pieces which are rigidly connected with each other via the gear transmission, an intermediate gear of the gear unit can be shifted axially thereby disengaging it from the gear unit so that the eye-pieces can be adjusted relative to one another. After this adjustment the intermediate gear must be shifted axially again and thus meshed with the rest of the gear-wheels. The individual adjustment of the eye-pieces carried out in such a manner is most troublesome, and it is not suitable for example for telescopes intended for military use.
A binocular telescope already exists having two separate focusing wheels arranged on the joint axis whereby each focusing wheel is connected to a focusing ring of an eye-piece via a corresponding toothed gear. The two focusing wheels are arranged so closely to one another that they can be mutually manipulated and resulting in synchronous focal length adjustment of the eye-pieces. If, in order to adjust the diopters, only one eye-piece has to be adjusted, it is only necessary to turn one focusing wheel. This arrangement is disadvantageous, however, in that, on the one hand, an accidental shift of the diopters can easily take place and, on the other hand, it cannot be guaranteed that both focusing gears are really turned through exactly the same angle when there is corresponding manipulation.
It is also known that a belt drive can be employed instead of the gear transmission for the purpose of transmitting rotary action of a focusing wheel to the focusing rings of the eye-pieces. It has already been suggested that one of the focusing rings be arranged on the eye-piece tube in such a manner that it is clamped on the latter by means of a screw-type cap in order to make adjustment of the eye-pieces relative to one another feasible. After loosening the screw cap, the belt drive can be manipulated, i.e., an eye-piece can be adjusted without the other eye-piece being driven along with it. The screw cap must be tightened after this adjustment. Also, in the case of this design, it is considered a disadvantage that comparatively troublesome manipulation is necessary for a diopter adjustment.